1. Technical Field
This disclosure is generally related to auxiliary power or bias voltage supplies, to efficiently provide supply or bias voltages from low input voltages. Such apparatus may, for example be useful in a wide variety of devices or systems, particularly those employing circuits with periodic high peak current power demands, for example, gate drive circuits employed in regulated switched mode power converters.
2. Description of the Related Art
Power converters are used to transform electrical energy, for example converting between alternating current (AC) and direct current (DC), adjusting (e.g., stepping up, stepping down) voltage levels and/or frequency.
Power converters take a large variety of forms. One of the most common forms is the switched-mode power converter or supply. Switched-mode power converters employ a switching regulator to efficiently convert voltage or current characteristics of electrical power. Switched-mode power converters typically employ storage components (e.g., inductor, transformer, capacitor) and switches that quickly switches between full ON and full OFF states, minimizing power losses. Voltage regulation may be achieved by varying the translated power by modulating the ratio of ON to OFF time or duty cycle. Various topologies for switched-mode power converters are well known in the art including non-isolated and isolated topologies, for example boost converters, buck converters, synchronous buck converters, buck-boost converters, and fly-back converters, and others.
In the interest of efficiency, digital logic technology is employing ever lower voltage logic levels. This requires power converters to deliver the lower voltages at higher current levels. To meet this requirement, power converters are employing more energy efficient designs. Power converters are also increasingly being located in close proximity to the load in as point of load (POL) converters in a POL scheme. These power converters must generate very low voltage levels (e.g., less than 1V) at increasingly higher current levels (e.g., greater than 10 A). These relatively high current levels may be difficult to achieve with a single power converter.
Manufacturers are also increasingly employing POL schemes in light of the widely varying voltage requirements in modern systems (e.g., computer systems). A POL scheme may be easier to design and/or fabricate, take up less area, and/or produce less interference than employing multiple different power buses. The POL schemes typically employ one or two power buses with a number of POL regulators located close to specific components or subsystems to be powered, for example microprocessors, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), volatile memory. The POL regulators adjust voltage to supply localized busses feeding the specific components or subsystems.
Many devices employ an auxiliary power or bias voltage power supply to provide supply voltages VCC, VSS. For example, switched mode power converters typically include an auxiliary power or bias voltage supply.
Existing approaches to auxiliary power or bias voltage supplies include those that generate unregulated voltages. Other existing approaches employ linear regulators or inefficient circuitry to provide regulated bias voltages. Existing approaches that generate unregulated bias supply voltages are generally not suitable for very low input voltage applications since the bias voltage that is generated is not high enough for most electronic circuitry. Existing approaches that employ a linear regulator to generate a regulated bias voltage suffer from relatively high inefficiency due to the dissipation of energy through the regulating element (e.g., series pass element). Additionally, a linear regulator is typically not able to supply multiple output bias voltages. Hence, multiple linear regulators are needed for applications that required multiple output bias voltages, adding substantial cost. These existing approaches also tend to have a somewhat limited operational temperature range.
For very or ultra low voltage inputs, an auxiliary power or bias voltage supply must generate a regulated voltage that is higher than the input voltage. It is also desirable that the auxiliary power or bias voltage supply operate efficiently throughout its voltage range, and be tolerant of dynamic load transients. It is also desirable that the auxiliary power or bias voltage supply operating frequency be compatible with the main supply. Further, an auxiliary power or bias voltage supply should also operate over a wide temperature range.
New approaches to auxiliary power or bias voltage supplies and the generation of bias supply voltages are desirable.